Set 2 large oven roasting bags or other sturdy bags in a roasting pan just large enough to hold the chickens. Set the chickens in the bags and pour in the brine. Turn the chickens to coat them completely with brine. Turn the chickens breast side down and tie the bags. Refrigerate for 24 hours.

Prepare the smoking mixture: Preheat the oven to 375 degrees F. In a bowl, combine the rice, sugar, tea, star anise, and chiles. Remove the chickens from the roasting pan. Line the pan with a double layer of heavy-duty aluminum foil. Scatter the tea mixture on the foil and set a rack in the pan. Remove the chickens from the brine and pat dry. Transfer the chickens to the rack, breast side up; be sure they do not touch the side of the pan. Tent heavy-duty foil over the chickens and seal all around the edge of the pan. Seal overlapping pieces of foil with tape.

Set the roasting pan over high heat and cook for 2 minutes. Reduce the heat to moderately low and cook for 5 minutes. Remove the pan from the heat and let stand for 3 minutes. Uncover the chickens and let rest for 10 minutes.

Transfer the chickens to a rimmed baking sheet, breast side up. Rub the chickens with vegetable oil, sprinkle with the Sichuan peppercorns, and season lightly with salt. Roast in the upper third of the oven for 35 minutes. Increase the oven temperature to 425 degrees F and continue to roast for about 35 minutes longer, until an instant-read thermometer inserted in the inner thighs registers 165 degrees F. Transfer the chickens to a carving board and let rest for 10 minutes.

Make the scallion-ginger sauce: In a bowl, combine the scallions, ginger, and oil and season with salt. Carve the chickens and serve with the sauce.